People with AIDS often get an eye infection caused by cytomegalovirus (CMV). The infection involves the retina and can cause loss of vision. However, treatment can help prevent loss of vision. The purpose of this study is to compare two treatments for CMV retinitis: 1) ganciclovir implant plus ganciclovir pills and 2) cidofovir injections. Although both drugs are approved by the FDA, this study is being done to answer questions as to which form of treatment is the best.